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popcount: use intrinsics and restructure defines

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This commit is contained in:
Matthew Barr 2016-05-20 15:30:29 +10:00
parent 142e74e8e6
commit 5234639736
1 changed files with 10 additions and 12 deletions
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22
src/util/popcount.h
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2015, Intel Corporation
* Copyright (c) 2015-2016, Intel Corporation
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
@ -38,21 +38,17 @@
// We have a native popcount where the compiler has defined __POPCNT__.
#if defined(__POPCNT__)
#define HAVE_POPCOUNT_INSTR
#endif
#if defined(_WIN32) && defined(__AVX__) // TODO: fix win preproc
#elif defined(_WIN32) && defined(__AVX__) // TODO: fix win preproc
#define HAVE_POPCOUNT_INSTR
#define __builtin_popcount __popcnt
#define __builtin_popcountll __popcnt64
#endif
static really_inline
u32 popcount32(u32 x) {
#if defined(HAVE_POPCOUNT_INSTR)
// Single-instruction builtin.
return (u32)__builtin_popcount(x);
return _mm_popcnt_u32(x);
#else
// Fast branch-free version from bit-twiddling hacks as most Intel
// Fast branch-free version from bit-twiddling hacks as older Intel
// processors do not have a POPCNT instruction.
x -= (x >> 1) & 0x55555555;
x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
@ -62,16 +58,18 @@ u32 popcount32(u32 x) {
static really_inline
u32 popcount64(u64a x) {
#if defined(HAVE_POPCOUNT_INSTR)
#if defined(ARCH_X86_64)
# if defined(HAVE_POPCOUNT_INSTR)
// Single-instruction builtin.
return (u32)__builtin_popcountll(x);
#elif defined(ARCH_X86_64)
// Fast branch-free version from bit-twiddling hacks as most Intel
return (u32)_mm_popcnt_u64(x);
# else
// Fast branch-free version from bit-twiddling hacks as older Intel
// processors do not have a POPCNT instruction.
x -= (x >> 1) & 0x5555555555555555;
x = (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333);
x = (x + (x >> 4)) & 0x0f0f0f0f0f0f0f0f;
return (x * 0x0101010101010101) >> 56;
# endif
#else
// Synthesise from two 32-bit cases.
return popcount32(x >> 32) + popcount32(x);